Micro Process Technology and Novel Process Windows –Three Intensification Fields Svetlana Borukhova and Volker Hessel - Process Intensification for Green Chemistry - page 99

Figure 4.5 Cross-section of laminated flow in an SAR mixer. Permission granted by RSC, [87].

microchannel sizes typical for micromixers, such a flow regime is only used for higher-
viscosity liquids such as glycerol solutions (Re 10) and not for water or organic solvents.

Above this regime, specially designed SAR micromixers can also be operated at a wide
range of Re by inducing chaotic advection within the channels. The main disadvantage of
the SAR mixer is the often-complex fabrication required to generate the necessary 3D
internal structure. The design introduced by Lim et al. consists of a 3D micromixer, named
the crossing manifold micromixer, in which almost complete mixing is achieved in 250 m m
[86].
The flow rearrangement pattern can be induced via incorporation of intersecting
microchannels within the main stream. The design of such a mixer (Figure 4.6) was
undertaken by He et al., and complete mixing was achieved in 0.4 seconds [55]. In a design
introduced by Sudarsan et al., centrifugal force can ensure splitting and recombining of the
flow [88]. This first allows vortices to be generated within a stream along the vertical plane,
then splits them into multiple substreams and later recombines them, yielding a multi-
compartment arrangement.

Figure 4.6 Planar SAR micromixer design based on constantly intersecting changing flow
patterns. Courtesy of ACS, [55].